In PyJWT 1.5.0 and below the invalid_strings
check in HMACAlgorithm.prepare_key
does not account for all PEM encoded public keys. Specifically, the PKCS1 PEM encoded format would be allowed because it is prefaced with the string -----BEGIN RSA PUBLIC KEY-----
which is not accounted for. This enables symmetric/asymmetric key confusion attacks against users using the PKCS1 PEM encoded public keys, which would allow an attacker to craft JWTs from scratch.
{ "nvd_published_at": "2017-08-24T16:29:00Z", "cwe_ids": [], "severity": "HIGH", "github_reviewed": true, "github_reviewed_at": "2022-09-12T14:50:37Z" }